<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>title</title>
</head>
<body>
    <script>
        var books= {
            name1:'《javaScript前端开发案例教程》',
            name2:'《Node.js核心基础教程》' , 
            name3:'《HTML5移动Web开发》'  
    };
    for(var i in books ){//遍历books对象:变量i为什么可以任取？
        console.log( books[i]);
    } 
    </script>
</body>
</html>